FACT Disrupts Nucleosome Structure by Binding H2A-H2B with Conserved Peptide Motifs

• Published in: Molecular cell 2015-10, Vol.60 (2), p.294-306
• Main Authors: Kemble, David J., McCullough, Laura L., Whitby, Frank G., Formosa, Tim, Hill, Christopher P.
• Format: Article
• Language: English
• Subjects: Amino Acid Motifs; Conserved Sequence; crystal structure; Crystallography, X-Ray; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Gene Expression Regulation, Fungal; High Mobility Group Proteins - chemistry; High Mobility Group Proteins - genetics; High Mobility Group Proteins - metabolism; histone binding; histone chaperone; Histones - chemistry; Histones - genetics; Histones - metabolism; Models, Molecular; Molecular Sequence Data; nucleosome reorganization; Nucleosomes - chemistry; Nucleosomes - metabolism; Protein Binding; Protein Multimerization; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Sequence Alignment; Spt16-Pob3; Transcription Factors - chemistry; Transcription Factors - genetics; Transcription Factors - metabolism; Transcriptional Elongation Factors - chemistry; Transcriptional Elongation Factors - genetics; Transcriptional Elongation Factors - metabolism
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2015.09.008

FACT, a heterodimer of Spt16 and Pob3, is an essential histone chaperone. We show that the H2A-H2B binding activity that is central to FACT function resides in short acidic regions near the C termini of each subunit. Mutations throughout these regions affect binding and cause correlated phenotypes that range from mild to lethal, with the largest individual contributions unexpectedly coming from an aromatic residue and a nearby carboxylate residue within each domain. Spt16 and Pob3 bind overlapping sites on H2A-H2B, and Spt16-Pob3 heterodimers simultaneously bind two H2A-H2B dimers, the same stoichiometry as the components of a nucleosome. An Spt16:H2A-H2B crystal structure explains the biochemical and genetic data, provides a model for Pob3 binding, and implies a mechanism for FACT reorganization that we confirm biochemically. Moreover, unexpected similarity to binding of ANP32E and Swr1 with H2A.Z-H2B reveals that diverse H2A-H2B chaperones use common mechanisms of histone binding and regulating nucleosome functions. [Display omitted] •Spt16 and Pob3 C-terminal peptides are primary determinants of H2A-H2B binding•Aromatic and acidic residues in natively disordered acidic domains mediate binding•FACT binds two H2A-H2B dimers using a mechanism similar to ANP32E and Swr1•FACT binding drives nucleosome reorganization by disrupting a DNA-histone interface Kemble et al. reveal a conserved binding motif in the FACT complex for H2A-H2B that is necessary for nucleosome reorganization and is present in other, unrelated histone binding factors.